ALTHOUGH both rhinitis and asthma occur without a recognized allergic mechanism, IgE-mediated inflammation is usually found in both diseases. It is estimated that 40 million Americans (nearly 25%) have asthma and other allergic diseases. Other figures compiled by the National Center for Health Statistics underscore the magnitude of this health burden.1 In fact, allergic rhinitis accounts for more than 3% of all office visits.1 The prevalence of the common allergic diseases2 is shown in Table 3-1.

ALLERGENS IN ALLERGIC DISEASESInhalant allergens are most frequently involved in allergic respiratory diseases, such as allergic rhinitis and asthma. These antigens, which directly impact on the respiratory mucosa, are usually derived from natural organic sources, such as house dust, pollens, mold spores, and insect and animal emanations. Chemicals and irritants from the workplace have been increasingly recognized as a cause of rhinitis, asthma, or both. A few aeroallergens have been